thx a lot.... Where i can find more information about iirc and when it is used
in comparison with the tick rate?
My question arrised when i was trying to see if i can reach a time accuracy
below 1ms in my linux box.... NTP uses IIRC or the tick rate?
Thx a lot
Quoting Neil Horman <nhorman@xxxxxxxxxx>:
> apalaios@xxxxxxxxxxxx wrote:
> > Hi...yesterday i was reading the understanding linux kernel and the linux
> kernel
> > development. I have found that at boot time the kernel programmes the irq0
> to a
> > tick rate of 1 ms for 2.6 linux kernel and 10ms for 2.4 kernel...
> >
> > Also the articles that i have read said that the kernel updates the system
> clock
> > each 1 msec. I was wondering then how the kernel is possible to keep
> > microsecond timestamps for the packets coming in an interface? How can
> calulate
> > the time when the basic timer is only at 1 millisecond?
> > I have also read for the
> >
> > struct timespec {
> > time_t tv_sec; /* seconds */
> > long tv_nsec; /* nanoseconds */
> > };
> >
> > timespec struct that has a nanosecond field.. How the kernel can insert
> data to
> > that field and how it can calculate the nanoseconds have passed??
> > Thx..as u can understand i am very confused about time related issues...so
> plz
> > shed as much ligh as u can..
> > Thx a lot Alex Paleos
> >
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> IIRC Most arches have a free running counter that has nanosecond
> granularity. You just read it when a packet arrives and can use that to
> calculate very small amounts of time.
>
> Neil
> --
> /***************************************************
> *Neil Horman
> *Software Engineer
> *Red Hat, Inc.
> *nhorman@xxxxxxxxxx
> *gpg keyid: 1024D / 0x92A74FA1
> *http://pgp.mit.edu
> ***************************************************/
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